This invention relates to a substrate dependence reducing agent useful as the constituent of a chemical amplified type positive- or negative-working resist composition used for production of semiconductor devices, etc., a resist composition containing said agent, and a pattern formation process using the resist composition.
In place of a source of i-line light (365 nm), a KrF excimer laser having a shorter output wavelength of 248 nm has recently come to be used as a light source for exposure used in a lithography process because of a demand for ultramicrofabrication caused with an enhancement of the degree of integration of semiconductor devices. Consequently, conventional dissolution-inhibiting type resists which require exposure at several hundreds milli-joule have become unusable for, for example, the following reasons: no high energy can be obtained because the excimer laser is used in place of a mercury vapor lamp; and the resists strongly absorb light (namely, they are poor in transmittance) at 248 nm. Therefore, there have come to be used chemical amplified type resists which have a high transmittance even at 248 nm and permits pattern formation by exposure at several tens milli-joule.
The chemical amplified type resists, however, tend to be affected by a substrate because they have a reaction mechanism in which a dissolution-inhibiting compound such as an alkali-insoluble compound or an alkali-insoluble polymer becomes alkali-soluble owing to exposure energy during pattern formation, i.e., a two-step reaction mechanism in which an acid is generated from a photosensitive compound, on account of the exposure energy, and a chemical reaction is caused by the generated acid, so that the alkali-insoluble compound or polymer becomes alkali-soluble. That is, the decrease of the exposure dose enhances the influence of a subtle difference of the exposure dose in the boundary surface portion of the substrate and the influence of a basic substance and water which are released from the substrate. Therefore, in device production using the chemical amplified type resist, it becomes impossible to attain a good profile of pattern by using a special substrate (e.g. TiN, BPSG, etc.) which has been extraordinarily disadvantageous. Such substrate dependence is a serious problem.
For solving this problem, there have been proposed resist compositions containing an organic carboxylic acid (for example, JP-A 9-6001, JP-A 9-6002, JP-A 9-6003 and European Patent Laid-Open No. 679951), and it has been reported that the resist compositions improve a profile of pattern on a special substrate. These resist compositions containing an organic carboxylic acid, however, are disadvantageous in that since the organic carboxylic acid is utilized for causing a chemical reaction to reduce the substrate dependence, the resist compositions are strongly acidic and hence deteriorated in performance characteristics during storage. For alleviating this disadvantage, a basic compound should be added in an amount larger than that required for neutralizing the organic carboxylic acid, resulting in causing problems such as a sensitivity decrease, etc.
Accordingly, there is desired the development of a highly sensitive resist composition which gives a pattern with an excellent profile even on a special substrate and has an excellent storage stability and a satisfactory throughput.